1. Field of the Invention
The invention relates generally to methods and devices for detecting wellbore and tool operating conditions while engaged in fishing or other downhole manipulation operations to remove a wellbore obstruction or in other non-drilling applications, especially in very deep and/or deviated wellbores.
2. Description of the Related Art
Devices are known for measurement-while-drilling (MWD) and logging-while-drilling (LWD) wherein certain borehole conditions are measured and either recorded within storage media within the wellbore or transmitted to the surface using encoded transmission techniques, such a frequency shift keying (FSK). Transmission may be accomplished via radio waves or fluid pulsing within drilling mud. The conditions measured typically include temperature, annulus pressure, drilling parameters, such as weight-on-bit (WOB), rotational speed of the drill bit and/or the drill string (RPMs), and the drilling fluid flow rate. An MWD or LWD sub is incorporated into the drill string above the bottom hole assembly and then operated during drilling operations. Examples of drilling systems that utilize MWD/LWD technology are described in U.S. Pat. Nos. 6,233,524 and 6,021,377, both of which are owned by the assignee of the present invention and are incorporated herein by reference.
Aside from typical drilling operations, there are other situations where it is helpful to have certain information relating to operation of the tool that is operating downhole and its environment. In very deep and/or high angle wellbores, it is difficult to verify details concerning the operation of the downhole tools through surface indications alone. For example, if one were attempting to remove a stuck section of casing in a deep and/or deviated wellbore using a rotary milling device, it would be very helpful to be able to measure the amount of torque induced proximate the milling device. Without an indication of the amount of torque induced proximate the milling device, the milling string can be overtorqued at the surface and the string between the milling tool and the surface will absorb the torque forces without effectively transmitting them to the milling tool. Overtorquing the tool string in this situation may lead to a shearing of the tool string below the surface, thereby creating an obstruction that is even more difficult to remove.
To the inventors' knowledge, there are no known, acceptable devices for providing useful downhole operating condition information, including torque, weight, compression, tension, speed of rotation, and direction of rotation, in non-drilling situations. Further, the use of standard MWD tools for such non-drilling applications is quite expensive. Current MWD tools are designed to obtain significant amounts of borehole information, much of which is not relevant outside of a drilling scenario. The devices for collecting this drilling specific information includes nuclear sensors, such as gamma ray tools for determining formation density, nuclear porosity and certain rock characteristics; resistivity sensors for determining formation resistivity, dielectric constant and the presence or absence of hydrocarbons; acoustic sensors for determining the acoustic porosity of the formation and the bed boundary in formation; and nuclear magnetic resonance sensors for determining the porosity and other petrophysical characteristics of the formation. To the inventors' knowledge, there is no known and acceptable “fit-for-purpose” tool wherein the sensor portion of the tool may be customized to detect those data that are important to the job at hand while not detecting irrelevant or less relevant information.
There is a need for improved devices and methods that are capable of providing operating condition information to the surface in non-drilling situations. There is also a need for improved methods and devices for accomplishing fishing and retrieval-type operations. Additionally, there is a need for improved methods and devices for accomplishing other non-drilling applications, such as underreaming, in-hole casing cutting and the like. The present invention addresses the problems of the prior art.